I have dual monitors. One is a 1280x1024 flat panel, and the other is a 1024x768 CRT. Until this morning, I did not realize that I could drive both from my nVidia card. After setting up TwinView, everything works great except for one thing: the CRT sometimes emits a high-pitched whistle/squeal. It is very annoying, and it gets worse when large white areas are displayed. Power-cycling the CRT or smacking it sometimes make the squeal go away temporarily.

This same problem occurred when the CRT was attached to the other video card (an ATI), and I solved it by placing the following modeline in the Monitor section for the CRT:

Further investigation reveals that I was actually overdriving the CRT slightly, and the nvidia driver was rejecting the custom modeline for this reason (because the PixelClock was exceeded).

The whistling happens at 75Hz. I can drive the monitor at 70Hz fine but then I can see the flicker.

'Option "UseEDID" "False" made the CRT work but hosed up the flat panel. It seems what I need to do is ignore EDID on the CRT but not the flat panel. Can this be done?

xorg.conf which was closest to working is attached.

For now I'm back to plain Xinerama with the CRT hanging off the ATI card, which is OK, but it's an old card so 3D and videos don't work on that screen (and in fact running 3D apps there causes a hard lockup).